Light emitting diodes (LEDs) are gaining wide acceptance in a variety of area-illumination applications such as in architectural lighting, residential illumination, industrial lighting, outdoor lighting, and the like.
A typical LED is made of semiconducting materials doped with impurities to create a p-n junction. As in other diodes, current flows easily from the p-side, or anode, to the n-side, or cathode, but not in the reverse direction. Charge-carriers such as electrons and holes may flow into the p-n junction from electrodes with different voltages. When an electron meets a hole, for example, it falls into a lower energy level and releases energy in the form of a photon.
For high-brightness applications, a large LED chip size is preferable. More importantly, with larger LED chip size, higher brightness may be achieved at much lower current density which leads to less degradation of efficacy. However simply increasing the die size of LEDs causes significant yield loss and thus hinders the adoption of big-chip LEDs.